Color filter substrate with black matrix on undercut groove and fabricating method thereof

ABSTRACT

A color filter substrate including a substrate, a black matrix layer and a color filter substrate layer is provided. The substrate has a plurality of grooves. The black matrix layer is disposed on the substrate between each two adjacent grooves, wherein the black matrix layer extends to the region above the groove from the edge of the groove and an undercut profile forms between the bottom of black matrix and the substrate. The color filter layer including a plurality of filter films separated is filled in the plurality of grooves and the plurality of filter films is separated from each other by the black matrix layer. In addition, a method of fabricating a color filter substrate is also provided. The above-mentioned color filter substrate and the fabricating method thereof can improve the quality and color uniformity of the color filter substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of patent application Ser. No.12/370,611, filed on Feb. 13, 2009, now allowed, which claims thepriority benefit of Taiwan application serial no. 97129839, filed onAug. 6, 2008. The entirety of each of the above-mentioned patentapplications is hereby incorporated by reference herein and made a partof this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a component of a display panel and amethod for fabricating thereof. More particularly, the present inventionrelates to a color filter and a method for fabricating thereof.

2. Description of Related Art

With the advantages of high resolution, small volume, light weight, lowdrive voltage, low power consumption, and a wide range of applications,the liquid crystal display (LCD) has replaced the cathode ray tube (CRT)as the mainstream of the new generation display. In general, the methodfor fabricating a color filter substrate of an LCD includes threephotolithography processes by using color photo resists with primarycolors, wherein three color filter films are formed in sequence incorresponding pixel regions on a substrate and form the color filtersubstrate. More specifically, the color filter films are formed bycoating color photo resists on the substrate. The method of coatingcolor photo resists is usually performing spin coating to uniformly coaton the substrate. Therefore, a great part of the color photo resist iswasted in the spin coating process and the fabricating cost isincreased. In addition, in order to uniformly distribute the color photoresists during the coating process, a large amount of organic solvent isgenerally used in the color photo resist. Other processes such as a softbake or a hard bake process are performed after the coating process tocure the color photo resist to form the color filter film.

A conventional technology which uses an inkjet printing (IJP) process toform a color filter substrate has been developed. The IJP process mayprint color inks of three primary colors to formed color filter films inpixel regions. Compared with the conventional photolithography processof fabricating color filter films, the IJP process may reduce costs ofmanufacturing and materials. For forming the color filter films, the IJPtechnology has advantages of saving fabricating cost and large areamanufacturing.

The conventional color filter substrate includes a black matrix layerand color filter films of the three primary colors, red, green, andblue. As shown in FIG. 1A, a black matrix player 120 is formed bycoating resin photo resist on the substrate and subsequent processessuch as soft bake, exposure, development, and hard bake are performed insequence to form the black matrix layer 120. Next, color ink is inkjetprinted in a pixel region P. In addition, a treatment process isgenerally performed after the black matrix layer is formed to preventthe color inks from overflowing onto the black matrix layer 120, causingcolor intermixing in the pixel. The surface of the black matrix layer120 has a hydrophobic characteristic after the treatment process suchthat the color inks would hardly adhere onto the black matrix layer 120and flow into the pixel region P.

However, no matter the black matrix layer 120 made of resin photo resistis fabricated by liquid photo resist coating or dry film attaching, theresin photo resist is usually subjected to the abovementioned treatmentprocess by an atmospheric pressure plasma process after exposure,development and hard bake, for example. Some scum 122 may easily remainat the intersection region between the black matrix layer 120 and thesubstrate 110 after the black matrix layer 120 has been bombarded byplasma. In addition, the scum 122 itself also has a hydrophobiccharacteristic, resulting in a situation that after color inks arefilled in the black matrix layer 120, the edges of the black matrixlayer 120 are not filled and thus a color filter layer 130 as shown inFIG. 1B is formed. As such, problems such as light leakage andnon-uniform colors may occur and reduce the display quality of the LCDpanel. Furthermore, as shown in FIG. 1B, after color inks are filled inthe pixel region, influencing factors such as material of the colorinks, surrounding environment, and surface tension of the black matrixlayer 120 cause the surface of the color filter film to form a convexsurface of non-uniform thickness on the substrate and further influencecolor performance.

SUMMARY OF THE INVENTION

The present invention provides a color filter substrate and afabricating method thereof which improves the problem that scum formedduring a plasma treatment process of the black matrix layer remains atthe intersection between a black matrix layer and a substrate, and causethe condition of non-completely filled pixel regions.

The color filter substrate of the present invention includes asubstrate, a black matrix layer, and a color filter layer. The substrateincludes a plurality of grooves with undercut profiles. The black matrixlayer is disposed on the substrate between each two adjacent grooves andextends from the edge of the grooves to the region above the groovessuch that the undercut profile is formed between the black matrix layerand the substrate. The color filter layer including a plurality of colorfilter films is filled in the grooves and the plurality of color filterfilms separated from each other is formed.

In one embodiment of the present invention, each of the abovementionedgrooves has a depth which, for example, uses a contact surface of thesubstrate and the black matrix layer as a standard and the maximum depthof each groove is substantially equal to one another. In one embodiment,the largest thickness of each filter film is smaller than the sum of thethickness of the black matrix layer and the maximum depth of the eachgroove. In one embodiment, the maximum depth is substantially less thanthe thickness of the black matrix layer and is substantially between 0.5μm and 2 μm, for example. In one embodiment, the maximum depth issubstantially 1 μm, for example.

In one embodiment of the present invention, the thickness of theabovementioned color filter layer is substantially less than thethickness of the black matrix layer.

In one embodiment of the present invention, the surfaces of theabovementioned filter films are planar except the area contacting withthe sides of the black matrix layer where liquid surface rises due tocapillary phenomenon of the inks.

In one embodiment of the present invention, a tangent line is formed onthe edge of each groove neighboring the substrate surface and an acuteangle is formed between the tangent line and a surface of the substratesurface.

In one embodiment of the present invention, the abovementioned grooveshave different depths and the surfaces of the filter films aresubstantially on a same plane.

In one embodiment of the present invention, the abovementioned grooveshave a first depth, a second depth, and a third depth. The filter filmsinclude a red filter film, a green filter film, and a blue filter film.The filter films with the same color are filled in grooves with the samedepth, and different colors are filled in grooves with the differentdepths. For example, the red filter film is filled in grooves with thefirst depth. The green filter film is filled in grooves with the seconddepth. The blue filter film is filled in grooves with the third depth.In one embodiment, the first depth and the second depth aresubstantially less than the third depth. The first depth issubstantially equal to the second depth. In another embodiment, thefirst depth and the second depth are substantially larger than the thirddepth. The first depth is substantially equal to the second depth. Inanother embodiment, the first depth is substantially smaller than thesecond depth. The second depth is substantially smaller than the thirddepth.

In one embodiment of the present invention, the abovementioned colorfilter substrate further includes a transparent electrode layer whichcovers the color filter layer and the black matrix layer.

In one embodiment of the present invention, the abovementioned colorfilter substrate further includes an active array layer disposed on thecolor filter layer and the black matrix layer.

The present invention further provides a method for fabricating a colorfilter substrate. The method includes the following steps. First, asubstrate is provided. A black matrix layer is formed thereon andseparates a plurality of pixel regions on the substrate. Afterward,grooves with undercut profiles are formed in the pixel regions of thesubstrate using the black matrix layer as a mask. Subsequently, atreatment process is performed on the surface of the black matrix layer.Next, the color filter layer is filled in the grooves using an inkjetmethod. The color filter layer is automatically separated at the groovesby the black matrix layer and forms a plurality of filter films.

In one embodiment of the present invention, the abovementioned method offorming the grooves in the pixel regions of the substrate includesperforming a wet etching process on the substrate. In one embodiment,the wet etching process includes using hydrofluoric acid (HF).

In one embodiment of the present invention, the treatment processincludes performing a plasma treatment process.

In one embodiment of the present invention, the abovementioned method offilling color filter layer includes inkjet printing (IJP) to fill colorinks in the groove in each pixel region.

In one embodiment of the present invention, the surfaces of theabovementioned filter films are substantially on a same plane.

In one embodiment of the present invention, the abovementioned method offorming the filter films in the grooves includes the following steps.First, a red filter film is filled in the grooves of a first part,wherein the grooves in the first part have a first depth. Afterward, agreen filter film is filled in the grooves of a second part, wherein thegrooves in the second part have a second depth. Next, a blue filter filmis filled in the remaining grooves, wherein the remaining grooves have athird depth. In one embodiment, a treatment process is further performedon the surface of the black matrix layer and the red filter film beforefilling the green filter film in the grooves with the second depth. Inone embodiment, a treatment process is further performed on the surfaceof the black matrix layer, the red filter film, and the green filterfilm before filling the blue filter film in the grooves with the thirddepth.

In one embodiment of the present invention, the part of the substrate inthe grooves exposed by the black matrix substrate, the red filter film,and the green filter film is removed using the black matrix substrate,the red filter film, and the green filter film as masks before fillingthe blue filter film in the grooves with the third depth so that theexposed grooves have. Then, the blue filter film is filled in thegrooves with the third depth and makes the surfaces of the filter filmsto be at a same height. The corresponding depths of the three colors aredifferent so the color filter films of various colors are different. Thethicknesses of the filter films may be adjusted based on the material oroptical characteristics thereof or according to the requirement of colorbrightness of the panel. For example, in this embodiment, the thicknessof the blue filter film is substantially larger than the thickness ofthe green filter film and the thickness of the green filter film issubstantially equal to the thickness of the red filter film. Inaddition, in another embodiment, the part of the substrate in thegrooves exposed by the black matrix substrate and the red filter film isremoved using the black matrix substrate and the red filter film as amask before filling the green filter film in the grooves with the seconddepth so that the exposed grooves have the second depth. As a result,the thickness of the blue filter film is substantially larger than thethickness of the green filter film and the thickness of the green filterfilm is substantially larger than the thickness of the red filter film.The surfaces of the filter films are at a same height.

According to a preferred embodiment of the present invention, the blackmatrix layer is first formed on the substrate. A plurality of grooveswith undercut profiles is formed in the regions separated by the blackmatrix layer on the substrate. As such, a color filter layer with a flatsurface may be formed after color inks are filled in the grooves.Furthermore, scum and the black matrix layer both treatedhydrophobically are not co-planar that results to an ineffectivehydrophobic tension between inks and scum. Therefore, color inks may becompletely filled in every entire pixel region, and thereby improve thequality and yield of the color filter. The LCD panel that uses thiscolor filter also has better display quality.

In order to make the aforementioned features and advantages of thepresent invention more comprehensible, several embodiments accompaniedwith figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A is a schematic diagram of a conventional black matrix layerformed on a substrate.

FIG. 1B is a schematic diagram of a sub-pixel of a conventional colorfilter.

FIG. 2A to FIG. 2D are schematic diagrams illustrating the flow of thefabricating process of the color filter according to the firstembodiment of the present invention.

FIG. 2E is another schematic diagram of a color filter of the presentinvention.

FIG. 3A and FIG. 3B illustrate the color filter according to the secondembodiment of the present invention.

FIG. 4A to FIG. 4E are flow charts of the fabricating process of thecolor filter as shown in FIG. 3A.

FIG. 5A to FIG. 5D are flow charts of the fabricating process of thecolor filter as shown in FIG. 3B.

FIG. 6A and FIG. 6B are cross-sectional schematic diagrams of LCD panelsusing a color filter of the present invention.

DESCRIPTION OF EMBODIMENTS

In the conventional fabricating process of a color filter substrate,during a treatment process after forming a black matrix layer, scum isgenerated at the edge of the black matrix layer, which affects a latercoating process of color inks. Therefore, in the present invention,grooves with undercut profiles separated from each other arerespectively formed in predetermined pixel regions on a substrate afterthe black matrix layer is formed. As such, even if scum is generated inlater fabricating processes, the hydrophobic scum and the black matrixlayer are not co-planar. The surface tension of the hydrophobic scum andthe surface tension of the hydrophobic black matrix layer havedifficulty in strengthening each other mutually. Therefore, color inksmay be filled into the pixel regions with ease and the color filterlayer thereby formed may completely fill the pixel regions. The blackmatrix layer extends from the edge of the grooves to the region abovethe grooves such that the undercut profile is formed between the blackmatrix layer and the substrate and most of the scum falls within theundercut profile of the grooves. As a result, the black matrix layerblocks the influence of the scum on the pixel display when using thecolor filter substrate for display. Thus, the technology provided in thepresent invention may overcome the problem of color inks being not ableto completely fill the pixel regions due to the influence of scum. Thepresent invention enables the color filer substrate to have betterquality and yield and further enables the LCD panel that uses the colorfilter substrate to have superior image display quality. Several methodsof fabricating a color filter substrate are provided below to illustratethe technical content of the present invention.

The First Embodiment

FIG. 2A to FIG. 2D are schematic diagrams illustrating the flow of thefabricating process of the color filter substrate according to the firstembodiment of the present invention. First referring to FIG. 2A, asubstrate 210 is provided. The material of the substrate 210 is atransparent material such as glass, quartz, or plastic. Next, a blackmatrix layer 220 is formed on the substrate 210, wherein the blackmatrix layer 220 separates a plurality of pixel regions P on thesubstrate 210. Specifically, a method of forming the black matrix layer220 on the substrate 210 includes first forming a light-shieldingmaterial layer (not shown) on the substrate 210 and then performing aphotolithography process on the light-shielding material layer (notshown) to pattern the light-shielding material layer (not shown). In thepresent embodiment, material of the light-shielding material layerincludes resin which has characteristics such as low transparent rate,small reflection factor, and photosensitivity. In addition, after thephotolithography process, a pre-baking process may further be performedon the black matrix layer 220. As such, the black matrix layer 220 maybe initially cured.

Afterward, as shown in FIG. 2B, grooves 230 with undercut profiles arerespectively formed in the pixel regions P on the substrate 210 usingthe black matrix layer 220 as a mask, wherein the grooves 230 areseparated from each other and arranged in array on the substrate 210,for example. The undercut profiles of the groove 230 have a plurality ofdifferent depths, for example, a slope formed by depth D and depth D′.The shape of the grooves 230 with the undercut profiles is a U shape,for example. Specifically, the undercut profiles of the grooves 230extend toward the direction of the black matrix layer 220 and partlyunderlay the black matrix layer 220. The method of forming the grooves230 with undercut profiles of a U shape includes performing a wetetching process using an etchant on the substrate 210, for example. Morespecifically, compared with the black matrix layer 220, the etchant hasa higher etching selectivity ratio on the substrate than the blackmatrix layer 220 so as to remove part of the substrate 210 and form thegrooves 230 in the pixel regions P. The etchant is hydrofluoric acid,for example, or other suitable etchant. It should be noted that becausethe wet etching process is an isotropic etching process, the grooves 230with undercut profiles may be formed as shown in the figures.

Referring to FIG. 2C, a treatment process is then performed on thesurface of the black matrix layer 220. In one embodiment, the treatmentprocess may be a plasma treatment process performed on the black matrixlayer 220. The plasma treatment process generally may use plasmacontaining fluorine to perform a process on the surface of the blackmatrix layer 220 so that the surface or side surface 220′ of the blackmatrix layer 220 becomes a hydrophobic layer with a hydrophobiccharacteristic or a hydrophobic surface 220S. Gas used to generatefluorine radicals by the plasma process is tetrafluoride (CF₄) or sulfurhexafluoride (SF₆), for example. The treatment process has no similareffect on the surface of the substrate 210. In other words, when thetreatment process is performed on the surface of the black matrix layer220, the grooves 230 in the pixel regions P will not become hydrophobic.Thus, the coating characteristic of color inks on the surface of thepixel regions is not affected. The phenomenon that color inks are notcompletely filled due to the hydrophobic characteristic of the groovesmay be prevented.

Furthermore, some scum may be generated during the treatment process.Because the grooves 230 of the present invention have the undercutprofiles, the black matrix layer 220 extends from the edge of thegrooves 230 (as the first depth D) toward the region above the undercutprofiles of the grooves (as the second depth D′). As a result, part ofthe grooves 230 extend into the projection area of part of the blackmatrix layer 220 so that part of the grooves 230 underlay part of theblack matrix layer 220, wherein the depth D is larger than the depth D′and the area of the undercut profiles is formed. Therefore, most of scumS will fall on the surface of the grooves 230 near the area under theblack matrix layer 220, i.e., the undercut profiles of the grooves 230.Compared with a position of scum 122 in a conventional structure asshown in FIG. 1A, the problem that color inks can not completely fillthe pixel regions because the scum 122 and the side surface of the blackmatrix layer 220 form a nearly right angle, generating a greaterhydrophobic tension and driving out wet color inks in prior art has beenresolved. Thus, in this embodiment, scum S is not adjacent to the sidesurface of the black matrix layer 220, which has been treated by ahydrophobic surface process, and the angle between scum S and the blackmatrix is smaller than 90 degree. Therefore, color inks may easily coverthe scum S and completely fill the entire pixel regions due to thesmaller hydrophobic surface tension compared with prior art.

More specifically, as shown in FIG. 2C, a tangent line is formed on theedge of the grooves 230 neighboring the surface of the substrate 210 andthe tangent line forms an acute angle θ with the surface of thesubstrate 210, wherein 0°<θ<90°. Between the side wall of the grooves230 and the black matrix layer 220 is a non-display region which enablesscum generated in later processes to more easily fall near theprojection position of the side surface 220′ of the black matrix layer220 onto the grooves 230. Therefore, the color filter substrate of thepresent invention may be able to use the undercut profiles U to preventscum S and prevent the problem that color inks fail to completely fillthe pixel regions, affecting color purity of the various color filterfilms. The present invention may further enhance color saturation of thecolor filter.

Referring to FIG. 2D, at this time, the black matrix layer 220 and thegrooves 230 with the undercut profiles U jointly form a wall 240 in aninkjet process. The wall 240 is between two adjacent pixel regions P.Next, after the wall 240 is formed, color inks are respectively filledin the grooves 230 of each pixel region P. A color filter layer 250 isautomatically separated into a plurality of filter films at the area ofthe grooves 230 through the black matrix layer 220 on the substrate 210.In detail, a method of forming the color filter layer 250 is, forexample, using an inkjet head to sequentially or simultaneously inkjetprint red, green, or blue color inks in the corresponding pixel regionsP. In addition, after forming the color filter layer 250, the color inksmay be further sequentially or simultaneously cured so that solvent inthe color filter layer 250 may be evaporated.

Furthermore, at the step of filling the color inks in the grooves 230,condition of non-completely filled color inks may still occur at theedge area of the grooves 230, e.g. areas of depth D″ smaller than D′.Because the unfilled edge areas of the grooves 230 is the intersectionbetween the pixel region and the black matrix layer 220, i.e.overlapping area X of the black matrix layer 220 and the grooves 230.The design of the grooves 230 makes the unfilled areas appear under theblack matrix layer 220 so the unfilled areas occurring in thenon-display region would not affect the color performance of color filersubstrate due to the shielding effect of the black matrix layer. As aresult, the quality of the color filter is not affected due to lightleakage does not occur.

After the color filter layer 250 is formed, a transparent electrodelayer 260 may further be formed to cover the color filter layer 250 andthe black matrix layer 220. Furthermore, a planar layer 254 mayselectively be formed between the color filter layer 250 and thetransparent electrode layer 260. In detail, material of the transparentelectrode layer 260 may be transparent and conductive materials such asindium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide(ZAO) which is formed on the color filter layer 250 and the black matrixlayer 220 using methods such as physical vapor deposition or sputtering.At this point, the fabrication of the color filter substrate 200 ismostly completed. In the present embodiment, disposition of a protectionlayer may further flatten the interface between the transparentelectrode layer 260 and the color filter layer 250 or fulfill otherrequirements.

In light of the above, FIG. 2D is a cross sectional schematic diagram ofthe color filter substrate of the first embodiment of the presentinvention. Specifically, the color filter substrate 200 mainly comprisesthe substrate 210, the black matrix layer 220, and the color filterlayer 250. The substrate 210 has a plurality of grooves 230 separatedfrom each other. The grooves 230 have the undercut profiles U. The blackmatrix layer 220 is disposed on the substrate 210 between each twoadjacent grooves 230. The black matrix layer 220 extends from the edgeof the grooves 230 to the area above the grooves 230 so that part of thegrooves 230 extend under part of the black matrix layer 220 and part ofthe grooves 230 undrelay part of the black matrix layer 220. The colorfilter layer 250 is filled in the grooves 230 and the filter filmsseparated from each other are formed respectively within the grooves230. In the present embodiment, the color filter layer 250 comprises aplurality of red filter films 250R, a plurality of green filter films250G, and a plurality of blue filter films 250B, for example. The redfilter films 250R, the green filter films 250G, and the blue filterfilms 250B may be arranged in a stripe type arrangement, a triangle typearrangement, a mosaic type arrangement, or a four pixel typearrangement. The present invention does not limit the type ofarrangement of the filter films in the color filter layer 250. Inaddition, In order to further increase color saturation in the colorfilter layer 250 and promote overall visual effects of the LCD panelthat uses the color filter substrate 200, the depth D of the grooves 230in the substrate 210 and the relationship between the thickness of thecolor filter layer 250 and the thickness of the black matrix layer 220may be adjusted according to product requirements and materialcharacteristics.

In detail, the black matrix layer 220 separates a plurality of pixelregions P on the substrate 210. The grooves 230 are formed by removingpart of the substrate 210 in the pixel regions P. The filter films ofvarious colors are then filled in the corresponding grooves 230. In thepresent embodiment, the depths D of the various filter films filled inthe grooves 230 are substantially equal to each other. Here, the depth Dis defined as the maximum depth of each groove 230. In practice, thedepth D of the grooves 230 may be adjusted according to the material ofthe filer films, the thickness of the black matrix layer 220, or theproduct requirement for color saturation so as to increase designmargin. For example, the depth D of the grooves 230 is substantiallysmaller than the thickness of the black matrix layer 220. The depth D ofthe grooves 230 is substantially between 0.5 μm and 2 μm, for example.In one embodiment, the depth D of the grooves 230 is substantially 1 μm.It should be pointed out that the depth D of the grooves 230 can bedefined from the contact surface of the substrate 210 and the blackmatrix layer 220 as a counting standard to the depth D of the grooves230.

It should be noted that the problem in the conventional technology thatcolor inks are not completely filled in the pixel regions P during theinkjet printing process may be overcome with the grooves 230 having theundercut profiles U in the color filter layer 250. The chances of thescum 122 causing the unfilled areas in the pixel regions P in prior artmay also be lowered. In detail, the grooves 230 of the present inventionhave the undercut profiles U. The black matrix layer 220 extends fromthe edge 230E of the grooves 230 to the area above the grooves 230 sothat the black matrix layer 220 partly overlap with the grooves 230 atthe area of the grooves where the depth is smaller than D, for example.Even if the scum S is generated in later processes, the scum S may moreeasily fall near the undercut profiles U of the grooves 230. Therefore,in this embodiment scum S is not adjacent to the side surface blackmatrix layer 220, which has been treated by a hydrophobic surfaceprocess. Therefore, color inks may more easily cover the scum S andcompletely fill the entire pixel regions due to the smaller hydrophobicsurface tension compared with prior art.

In light of the above, in the color filer layer 250 of the presentinvention, the filter films are formed in each of the grooves 230 usingan inkjet printing process, for example. Side walls of the black matrixlayer 220 and the grooves 230 may together play a role of wall 240between the filter films in later processes. As a result, the height ofthe wall 240 is larger than the thickness of the filter films so theproblem of intermixing of colors in the pixel regions P may be avoidedin the inkjet printing process, and thus the saturation of the jettedcolors in the color filter layer 250 is increased. In other words, inthe present embodiment, the largest thickness of the filter films issmaller than the sum of the thickness of the black matrix layer and thedepth D of the grooves 230. Therefore, the thickness of the color filterlayer 250 of the present invention may substantially larger than thethickness of the black matrix layer 220 without colors intermixing. Inother words, the present invention uses the thickness of the filterfilms of various colors to increase color saturation of the variouscolors. Furthermore, the problem of intermixing of colors does not occurin the actual process of increasing thickness of the filter films.

Furthermore, as shown in FIG. 2D, the color filter layer 250 is filledin the grooves 230. During the filling process of the color inks byinkjet printing, the black matrix layer 220 is higher than the surfaceof the wet color inks so that most of the display area in pixel region Pforms a substantially planar surface 250S except the surrounding regionof the filter films adjacent to the black matrix layer 220. The reasonis that the liquid surface 250S of wet color ink rises from the sidewall of the black matrix layer 220 due to capillary force. Therefore,the color filter layer 250 of the present invention has better thicknessuniformity than the conventional color filter layer 130 (as shown inFIG. 1B) and further has better color uniformity. In detail, the extremevalue of thickness (e.g. the largest thickness) of the color filterlayer 130 (as shown in FIG. 1B) which has a convex surface appearing inthe center of the pixel region P, a main performance area of the displayarea. However, the thickness limit (e.g. the smallest thickness) of thecolor filter layer 250 which has a concave surface appears in the twosides of the pixel region P which is an edge performance area of thedisplay area. Therefore, as compared with the conventional color filterlayer 130, the color filter layer 250 of the present invention hasbetter color uniformity.

It should be noted that the shape of the grooves of the presentinvention is not limited to be the abovementioned U shape. For example,the shape of the grooves on the substrate may also be as shown in FIG.2E. The abovementioned 0 may also be an obtuse angle, wherein 90°<θ<180°as shown with the grooves 230A in FIG. 2E. The design of the grooves mayalso be as shown with the grooves 230B in FIG. 2E. Peripheral surface Yof the grooves 230B under the black matrix layer 220 may also be a stairshape or irregular geometric shape, which is not limited by the presentinvention herein. That is, the substrate of the present inventionincludes the grooves with the undercut profiles. The black matrix layer220 extends to the area above the grooves adjacent to the substrate 210.Therefore, a containing space is formed between the black matrix layer220 and the grooves so that the color inks may be disposed in thecontaining space. Part of the grooves and part of the black matrix layeroverlap so there is no effect from the scum S adjacent to the side wallof the black matrix layer 220 which has bee treated by a hydrophobicsurface process. As a result, quality and color saturation of the colorfilter substrate 200 are effectively increased.

Continuing from the above embodiment, filter films of various colors mayhave different material characteristics in practice. Thus, the depth Dof the grooves 230 in the present invention may be adjusted according tovarious colors and various types of materials of the filter films. Thecolor performance of the filer films of various colors may then bettersatisfy user requirements and further increase overall visual effects ofthe LCD panel that uses the color filter. Several color filters withgrooves having different depths are illustrated as examples below.

The Second Embodiment

FIG. 3A and FIG. 3B further illustrate the color filter substrateaccording to the second embodiment of the present invention. Referringto FIG. 3A and FIG. 3B, for the purpose of simplification, similarcomponents to those shown in FIG. 2D will not be illustrated again inthe present embodiment. Compared with the abovementioned embodiment,grooves 230 that filter films of various colors are filled in havedifferent depths in color filter substrates 300 and 400 of the presentembodiment. In detail, the depths of the grooves 230 in the color filtersubstrates 300 and 400 of the present embodiment may be divided into afirst depth D1, a second depth D2, and a third depth D3. For example,red filter films 250R are filled in the grooves 230 with the first depthD1, green filter films 250G are filled in the grooves 230 with thesecond depth D2, and blue filter films 250B are filled in the grooves230 with the third depth D3. In the present embodiment, the surfaces ofthe filter films are substantially on a same plane, and the first depthD1, the second depth D2, and the third depth D3 is respectively presentsthe maximum value of depth in corresponding groove.

First referring to FIG. 3A, the first depth D1 of the grooves 230 of thecolor filter substrate 300 is substantially smaller than the seconddepth D2 and the second depth D2 is substantially smaller than the thirddepth D3. In other words, D1<D2<D3. In the present embodiment, thesurfaces of the red filter film 250R, the green filter film 250G, andthe blue filter film 250B are substantially on a same plane, which isnot limited by the present invention herein, however. As shown in FIG.3A, the thickness of the red filter film 250R is smaller than thethickness of the green filter film 250G and the thickness of the greenfilter film 250G is smaller than the thickness of the blue filter film250B.

Referring to FIG. 3B, the first depth D1 of the grooves 230 of the colorfilter and the second depth D2 are substantially smaller than the thirddepth D3 and the first depth D1 is substantially equal to the seconddepth D2. In other words, D1=D2<D3. In the present embodiment, thethickness of the red filter film 250R is substantially equal to thethickness of the green filter film 250G and the thickness of the bluefilter film is substantially larger than the thickness of the red filterfilm 250R and the thickness of the green filter film 250G. For example,the thickness of the blue filter film is about 1.9 μm and the thicknessof the red filter film 250R and the green filter film 250G is about 1.8μm. Certainly, in another embodiment, the relationship between the firstdepth D1, the second depth D2, and the third depth D3 may also beD1=D2>D3. Therefore, the present invention does not limit the depth ofthe grooves 230, the thickness of the filter films, the depthrelationship among the grooves 230, and the surface height relationshipand the thickness relationship among the filter films, which may be setaccording to material characteristics of the color filter layer 250 andproduct design requirements.

In addition, taking the color filter substrate 300 in FIG. 3A as anexample, a method for fabricating of a color filter substrate isprovided below and illustrated in the same manner as FIGS. 2A-2D. FIG.4A to FIG. 4E are flow charts of the fabricating process of the colorfilter substrate as shown in FIG. 3A.

For the purpose of simplification, fabricating processes similar tothose in FIG. 2A to FIG. 2D are not illustrated again in the following.As shown in FIG. 4B, compared with the abovementioned embodiment, in thepresent embodiment, after forming grooves 230 of a first depth D1, a redfilter film 250R is formed in the grooves 230 of a first part P1,wherein the method of forming the red filter film 250R is the same asmentioned in previous sections and will not be further illustratedhereinafter. Next, part of a substrate 210 exposed by a black matrixlayer 220 and the red filter film 250R is removed using the black matrixlayer 220 and the red filter film 250R as a mask so that the exposedgrooves 230 have a second depth D2. The abovementioned method ofremoving part of the substrate 210 is, for example, performing a wetetching process using hydrofluoric acid (HF).

Then, as shown in FIG. 4C, after forming the grooves 230 with the seconddepth D2, a green filter film 250G is filled in the grooves 230 of asecond part P2. Subsequently, as shown in FIG. 4D, part of the substrate210 in the grooves 230 exposed by the black matrix layer 220, the redfilter film 250R, and the green filter film 250G is removed using theblack matrix layer 220, the red filter film 250R, and the green filterfilm 250G as a mask so that the exposed substrate 210 has a third depthD3. The method of removing part of the substrate 210 is, for example,performing a wet etching process using hydrofluoric acid (HF). Next, asshown in FIG. 4E, after forming the grooves 230 with the third depth D3,a blue filter film 250B is filled in the remaining grooves 230, as shownthe grooves 230 of a third part P3 in FIG. 4E. As such, the color filtersubstrate 300 as in FIG. 3A is formed, wherein the thickness of the bluefilter film 250B is substantially larger than the thickness of the greenfilter film 250G and the thickness of the green filter film 250G issubstantially larger than the thickness of the red filter film 250R.

It should be noted that before the step of filling the green filter film250G in the grooves 230 with the second depth D2 as shown in FIG. 4C, atreatment process (not shown) may selectively be performed on thesurfaces of the black matrix layer 220 and the red filter film 250R.Similarly, before the step of filling the blue filter film 250B in thegrooves 230 with the third depth D3 as shown in FIG. 4E, a treatmentprocess (not shown) may selectively be performed on the surfaces of theblack matrix layer 220, the red filter film 250R, and the green filterfilm 250G. The method of performing the treatment process is similar tothat mentioned in the first embodiment, which will not be furtherillustrated hereinafter.

FIG. 5A to FIG. 5D are flow charts of the fabricating process of thecolor filter substrate as shown in FIG. 3B. The fabricating method ofFIGS. 5A-5D is similar to that of FIGS. 4A-4E with the main differencelying in that grooves 230 with a second depth D2 are not formed in acolor filter substrate 400 of the present embodiment. In other words, inthe present embodiment, the depths D1 and D2 of the grooves that the redfilter film 250R and the green filter film 250G are filled in aresubstantially equal to each other. Thus, the thickness of the bluefilter film 250B is substantially larger than the thickness of the greenfilter film 250G and the thickness of the green filter film 250G issubstantially equal to the thickness of the red filter film 250R.

It should be noted that the present invention does not limit the surfaceheights of the filter films of various colors to be equal. When colorsaturation of the color filter needs to be adjusted by usingsingle-color filter films of different thicknesses, the thicknesses ofthe filter films in the present invention may be adjusted using grooves230 with different depths D. The surface heights of the filter filmswith different thicknesses may align with one another. Thus, aprotection layer which is used flatten the uneven surface of the colorfilter layer 250 in some applications of the color filter in the presentembodiment can be omitted or a step of flattening with mechanicalpolishing can also be omitted. As such, not only is the colorperformance of the color filter increased but the fabricating processesare also simplified and the manufacturing costs are lowered. The grooves230 with the undercut profiles U are adopted in the above twoembodiments to overcome the problem in the conventional technology thatcolor inks can not completely fill the pixel regions P.

The color filter substrate of the present embodiment is fabricated withthe method in the abovementioned embodiments, for example.Alternatively, the fabricating processes and the shape of the grooves230 with the undercut profiles U can be adjusted according to actualconditions and the material of the color filter layer 250 and thefabricating processes thereof are not limited by the present inventionherein. Any fabricating methods in which grooves 230 with undercutprofiles U are formed on a substrate 210 to avoid scum S or to preventthe problem that color inks can not completely fill pixel regions P fallwith the protection scope claimed in the present invention.

FIG. 6A and FIG. 6B are cross-sectional schematic diagrams of LCD panelsusing a color filter substrate of the present invention. An LCD panel500 includes an array substrate 510, a color filter substrate 520, and aliquid crystal layer 530. The color filter substrate 520 is arrangedopposite to the array substrate 510, and the liquid crystal layer 530 issandwiched between the array substrate 510 and the color filtersubstrate 520. The color filter substrate 520 adopted here may be thecolor filter substrate disclosed in abovementioned embodiments or otherembodiments. First, referring to FIG. 6A, in practical applicationaspects, the color filter substrate 520 may further include atransparent electrode layer 260 which covers a color filter layer 250and a black matrix layer 220. Voltage difference between the transparentelectrode layer 260 and pixel electrodes of the thin film transistors onthe array substrate 510 enables liquid crystal molecules in the liquidcrystal layer 530 to rotate by different degrees. The LCD panel iscapable of full color display incorporating with the color filter layer250.

Referring to FIG. 6B, in another application aspect, an active devicearray 640 may be directly disposed on the color filter layer 250 and theblack matrix layer 220 to form an array on color filter substrate (AOC)610. The AOC substrate 610, an opposed substrate 620 having a commonelectrode 622, and a liquid crystal layer 630 therebetween constitute anLCD panel 600 capable of full color display, as shown in FIG. 6B.

In summary, in the present invention, grooves with undercut profiles areformed on the substrate to form a color filter layer after color inksare filled in the grooves. In addition, the problem of scum may beovercome. Therefore, after a later treatment process, the problem thatcolor inks can not completely fill pixel regions can be overcome andquality and yield can be further raised. In addition, an LCD that usesthe color filter of the present invention may also have better displayquality.

Although the present invention has been disclosed by the aboveembodiments, they are not intended to limit the present invention. Thoseskilled in the art may make some modifications and alterations withoutdeparting from the spirit and scope of the present invention. Therefore,the protection range of the present invention falls in the appendedclaims.

What is claimed is:
 1. A method for fabricating a color filtersubstrate, comprising: providing a substrate having a black matrix layerformed thereon, wherein the black matrix layer separates a plurality ofpixel regions on the substrate and is not a part of the substrate; usingthe black matrix layer as a mask and respectively forming a groove withan undercut profile in each pixel region, wherein the grooves face theblack matrix layer and part of the black matrix layer overlaps with partof the grooves, performing a treatment process on the surface of theblack matrix layer; and filling a color filter layer only in thegrooves, wherein the color filter layer includes a plurality of filterfilms separated by the black matrix layer.
 2. The method according toclaim 1, wherein the black matrix layer is not a part of the substrate,the grooves face the black matrix layer, and the color filter layerfilled only in the grooves of the substrate.
 3. The method according toclaim 1, wherein the step of forming the groove with the undercutprofile in the each pixel region comprises performing a wet etchingprocess on the substrate.
 4. The method according to claim 3, whereinthe wet etching process comprises using hydrofluoric acid (HF) as anetchant.
 5. The method according to claim 1, wherein the treatmentprocess comprises a plasma treatment process.
 6. The method according toclaim 1, wherein the step of filling the color filter layer in thegrooves comprises performing an inkjet printing process to fill colorinks in the grooves in the pixel regions.
 7. The method according toclaim 1, wherein surfaces of the filter films are substantially on asame plane.
 8. The method according to claim 1, wherein the step offilling the color filter layer in the grooves comprises: filling a redfilter film in the grooves of a first part, wherein the grooves of thefirst part have a first depth; filling a green filter film in thegrooves of a second part, wherein the grooves of the second part have asecond depth; and filling a blue filter film in the remaining grooves,wherein the remaining grooves have a third depth.
 9. The methodaccording to claim 8, wherein the step further comprises a treatmentprocess performed on the surfaces of the black matrix layer and the redfilter film before filling the green filter film in the grooves with thesecond depth.
 10. The method according to claim 8, wherein the stepfurther comprises a treatment process performed on the surfaces of theblack matrix layer, the red filter film, and the green filter filmbefore filling the blue filter film in the grooves with the third depth.11. The method according to claim 8, wherein the step further comprisesusing the black matrix layer, the red filter film, and the green filterfilm as a mask to remove part of the substrate in the remaining groovesexposed by the black matrix layer, the red filter film, and the greenfilter film before filling the blue filter film in the grooves with thethird depth.
 12. The method according to claim 11, wherein a thicknessof the blue filter film is substantially larger than a thickness of thegreen filter film and a thickness of the green filter film issubstantially equal to a thickness of the red filter film.
 13. Themethod according to claim 11, wherein the step further comprises usingthe black matrix layer and the red filter film as a mask to remove partof the substrate in the grooves exposed by the black matrix layer andthe red filter film before filling the green filter film in the grooveswith the second depth.
 14. The method according to claim 13, wherein athickness of the blue filter film is substantially larger than athickness of the green filter film and a thickness of the green filterfilm is substantially larger than a thickness of the red filter film.